The aim of this project is characterize schistosome surface molecules relevant to immunity, to analyze the genome of the parasite in relation to specific biological properties of the organism and to clone important schistosome immunogens. A. Molecular biology of paromyosin. In order to complete the nucleotide sequence of the paramyosin immunogen from S. mansoni, several genomic clones were isolated. In related studies, paramyosin from S. japonicum was cloned from a gamma gt-11 expression library. B. Molecular analysis of hycanthone resistance. Further restriction fragment length polymorphisms (RFLP) were identified in the DNA of schistosomes with experimentally induced resistance to hycanthone using different restriction enzymes. The RFLP's appeared to correlate with resistance since they re- occurred when a new resistant line was derived from the drug sensitive parent. In addition, differences were noted in the in vitro translation products of mRNA from drug sensitive and resistant lines. C. Autologous control of complement activation by the schistosome membrane. The aim of this new project is to understand how schistosomes are able to control activation of the alternative complement pathway (ACP) of the vertebrate host. It was shown that this control is autologous, i.e., worms recovered from one host fail to activate complement of that species but do activate complement of unrelated species. Moreover, treatment with either neuraminidose or phospholipase C was shown to convert schistosomes into activators of autologous complement. The data suggests that the molecules required for control of autologous complement activation are acquired by the schistosome membrane from the host.